I think turn based vs real time relates to the actual amount of independent battles you are going to fight. The amount of killing (every screen in fact) in DD reflects the fact that there is not a whole lot of strategy involved in the actual combat phase but more in what you do -before- the fight (weapons,eq,skills). Also even if there were strategy, the battles would have need to be reduced and "replaced" by stronger but less frequent mobs.
Wizardry 8 for example threw you into turn based combat -every- single battle.
Every battle did require alot of effort and thought and rarely it was a matter of hack and slash. You -had- to pull stunts like casting blindness and spelling yourself up before every encounter, things i only actually use on bosses in games like Baldur's gate, Diablo etc. Where Wizardry imho messed up was they gave you an encounter every screen almost, you would walk one step and you're in turn based combat, when you just want to run to the next town to get supplies. In the end it becomes a huge frustration.
Arcanum did an interesting move with the option of both turn based and real time. Problem was in real time it was actually just simply too fast, and basically they replaced the "pause" option with a turn based option, which in the end amounts to the exact same thing. I would press "space" and go into turn based, then click to do my specific spell, when i see i'm winning i would press space and let it continue in real time. Arcanum had alot of strategy involved mainly because every single battle you could possibly run out of stamina and fall uncounscious, even fighting a rat could cause it..falling uncounscious basically meant death if you didn't have other party members to revive you.
So it must be a balance between two big factors.
(1) Amount of encounters
(2) Amount of resources required during each encounter (This includes the party
vs solo grouped situation)
If it's mass destruction sprees where you can run around killing 100s of mobs without needing to heal, turn based will fail. If every battle is potentially a boss mob, which requires you to use even the smallest advantage, got then turn based will almost be required, although pause features is a nice midway.
So i'd say, as in Baldur's Gate where you had alot less encounters than in DD (imho) but still alot of encounters that were plain hack'n'slash would be perfect for the "pause" feature, turn based would be annoying there as there's not really enough "crunch" battles.
Only realtime RPG combat system i liked so far was in Blade of Darkness, although the game wasn't considered an RPG but more similar to Rune. Gothic
had a similar combat system going although not as complex, but was alot of fun.
(If you don't knwo what i'm talking about, in short, you went into combat mode just like DD, but then it became something like Mortal Kombat where you could make special moves, had to dodge attacks, shield blocking, ducking, and timing your attack) This requires 3D though, not sure how it can be applied on 2D without a Final Fantasy style of "switching" or "zooming" into battle. This obviously depends on amount of encounters too, less encounters but more life threatening encounteres are required.
